Aileen
I assume that you are aware of the post on tis family on the IGI
http://www.familysearch.org/eng/Search/frameset_search.aspboth Ann and Sarah Verner are lsited as married to the Pratts you mention.
It seems that they may have all died in South Australia which is unfortunatyely not online. SKS may be able to look up the death sof all four for you.
there is a cemetery listing for
Thoimas Pratt 1887
James Prat 1891
Sarah Pratt 1891 and 1926 the latter matches the info on the IGI
the only Ann was 1917 for Ann Elizabeth
http://www.saghs.org.au/graves.htmthey also offer a research service,
PRATT, ANN
Willaston Cemetery
Plot/Grave/Niche 40 O 1
lived at REEVES PLAINS
71 yrs
Date of Burial 23/05/1905
Minister Officiating REV T G WHITE
Burial/Order Number 2140
and in the same grave:
PRATT, JAMES
Willaston Cemetery
Plot/Grave/Niche 41 O 1
lived REEVES PLAINS
Age 79 yrs
Date of Burial 29/03/1909
Minister Officiating REV W REED
again same grave so a son???
PRATT, JOHN JAMES
Cemetery Willaston
Plot/Grave/Niche 40 O 1
lived GAWLER
Age 70 yrs
Date of Burial 23/03/1945 0:00
Minister Officiating REV. TREGILGAS
Grave Depth REOPEN
Funeral Director TAYLOR & FORGIE
Burial/Order Number 4344
Burial/Order Number 2343
appears to be several Pratts in Willaston
http://www.familyhistorysa.info/births-marriages-deaths/cemeteries/#CCand another site:
http://www.centennialpark.org/ has a verner Pratt in its listing.
with dates etc you may be able to look at deaath registrations more easily
Robyn in Wodonga